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1.
A license is a document that grants the bearer permission to engage in an activity or occupation that is otherwise considered illegal.

If you pay "tribute" to a government agency for their protection and friendship they will issue you a "license" to fish, hunt, drive, marry etc with impunity.

A method of the "state" exercising control of the populace.
cop: "Show me your license!"
driver: "I don't have one."
cop: "You're under arrest..(enter standard Miranda warning)"
by FN64GR September 29, 2006
 
2.
According to the dictionary, one set of definitions of 'license' is
"1. Lack of due restraint; excessive freedom: “When liberty becomes license, dictatorship is near” (Will Durant).
2. Heedlessness for the precepts of proper behavior; licentiousness."

The definition of 'license' that is synonymous with 'licentious' evolved from a very different definition:

"1. a. Official or legal permission to do or own a specified thing. See synonyms at permission.
b. A document, plate, or tag that is issued as proof of official or legal permission: a driver's license.
2. Deviation from normal rules, practices, or methods in order to achieve a certain end or effect."
These meanings are derived from "Middle English licence, from Old French, from Medieval Latin licentia, authorization, from Latin, freedom, from licens, licent-, present participle of licere, to be permitted."
License in the context that I want to focus on in related definitions such as libertarian and libertine is the lack of proper restraint or licentiousness.
Defenders of liberty have traditionally gone to great lengths to distance liberty from license. Tragically, modern leftist liberals and modal libertarians have conflated the the two. License is a perversion of liberty that has morphed into its opposite.
Modal libertarian: I love to exercise my liberty by watching some porn while I smoke pot.

Paleo-libertarian: You are confusing liberty and license.
by Tex in Tex July 10, 2008
 
3.
A piece of worthless, meaningless plastic, usually with ones picture and some personal information. If you have one, it means you spend time @ the DMV like a fucking idiot taking tests and what not. If you dont it means you r a mexican or another minortity (not white trash) and dont feel that it is neccesary and wont get cought without one.
Adrian: I got pulled over again, and I still dont have a license.
Andy: Y the cops always tryn' to catch you ridin' dirty?
Adrian: Cause' of the color of my skin.
by Ginger H. Ater January 31, 2007